[perf] Fix fallback for defaultBugURLTemplate.
[perf] Fix fallback for defaultBugURLTemplate.

Change-Id: I3d8c37f6645d40260ea57f379ef132cd384cddf7
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/315416
Reviewed-by: Joe Gregorio <b9cf2471ff6d33504cafe8e6f356b732b2cadced@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot